Since late March, Rihanna, 21, has been trying to recover the borrowed jewelry from the LAPD, who took the items into evidence in their investigation.

"Since there appears to be no evidentiary value to the continued holding of this jewelry ... we respectfully [ask] the court to order the return of this property to [Rihanna] without further delay," her lawyer Donald Etra wrote in a court request filed earlier this week.

The items were described as two yellow metal hoop earrings with white stones; one yellow metal ring with white stones and green stones; and two yellow metal rings with white stones.

"If the DA doesn't need the items, and the LAPD doesn't need the items, there's no reason why they shouldn't be returned," Etra tells PEOPLE.

A source adds that Rihanna also borrowed a Gucci dress for the Feb. 7 Clive Davis Pre-Grammy Party she attended, which also has not been returned.

Etra states in the documents that the owners of the jewelry were going to hold Rihanna liable if the accessories weren't returned, with the total cost and damages related to their late return as more than $1.4 million.

According to the court papers, the LAPD detective on the case referred Etra to the prosecutor on the case, who apparently has not responded to requests for the jewelry's return.

"At this stage, we're not even sure what evidence is going to be entered into the case," DA spokeswoman Sandi Gibbons tells PEOPLE. "For now, we don't have any further comment on this matter."